What is notable about lymphoid tissue?
Lymphoid tissue: The part of the body's immune system that is important for the immune response and helps protect it from infection and foreign bodies. Lymphoid tissue is present throughout the body and includes the lymph nodes, spleen, tonsils, adenoids, and other structures.
What are the primary and secondary lymphoid tissues?
• Primary lymphoid organs—include bone marrow and thymus—are sites where immune cells develop from immature precursors. • Secondary lymphoid organs—include spleen, lymph nodes, and specialized sites in the gut and other mucosal tissues—sites where the mature antigen-specific lymphocytes first encounter antigen
What is lymphoid tissue and where is it found?
The most highly organized lymphoid tissues are in the thymus and lymph nodes, which are well-defined encapsulated organs with easily identifiable architectures. In the spleen (a soft, purplish organ lying high in the abdomen), the lymphoid tissue is a cylinder of loosely organized cells surrounding small arteries.
What is the main function of the lymphatic system?
What Is the Main Function of the Lymphatic System? Center The lymphatic system serves as the body’s “sewage system” that filters blood and plays a role in immune responses.
What is the role of lymphoid tissue?
Lymphoid tissues have a unique role in the organization and function of the adaptive immune system. Mechanisms driving the development of these tissues have fascinated immunologists for the last 175 years. In this review, we will initially focus on historical literature describing lymph node (LN) anlage development and then on the contemporary understanding of the molecular mechanisms driving LN and Peyer's patch (PP) formation. Utilizing transgenic reporters and gene knockout mice, the interplay between hematopoietic inducer cells and stromal organizer cells has been shown to have a key role in the development and organization of the lymphoid tissues. Although PPs and LNs share many similarities in their development, key differences in the molecular requirements for their development have recently emerged.
How are lymphoid organs connected?
The lymphoid organs and tissues are connected by both the blood circulation and the lymphatic system. All cells in the body are bathed by nutrient-rich interstitial fluid, which is blood plasma that, under the pressure of the circulation, leaks from the capillaries into spaces between cells. Ninety percent of this fluid returns to the circulation via the venules, but 10% filters slowly through the tissues and eventually enters a network of tiny blind-ended channels known as the lymphatic capillaries, where it becomes known as lymph ( Fig. 3-10 ). The overlapping structure of the endothelial cells lining the capillaries creates specialized pores that allow high molecular weight substances such as proteins, fats, and even leukocytes and microbes to enter into the lymphatic capillaries with the lymph. Valves in the lymphatic capillaries ensure that the lymph and its cellular contents move only forward as the lymphatic capillaries collect into progressively larger lymphatic vessels. These vessels in turn connect with one of two large lymphatic trunks called the right lymphatic duct and the thoracic (or left lymphatic) duct ( Fig. 3-11 ). The right lymphatic duct drains the right upper body, while the entire lower body drains into the cisterna chyli at the base of the thoracic duct. Lymph from the left upper body also enters the thoracic duct. The right lymphatic duct empties the lymph into the right subclavian vein of the blood circulation, while the thoracic duct connects with the left subclavian vein.
What are the cells in the ibalt structure?
The typical iBALT structure consists of separate T and B cell areas accompanied by the presence of specific cell populations, such as follicular dendritic cells (FDCs), resident dendritic cells (DCs), high endothelial venules, and lymphatics [55,62]. Resident DCs within iBALT may present antigens, and FDCs are needed for the development of proper B cell follicles [56]. CD11c + DCs are involved in the maintenance of the iBALT structure [63]. Massive lymphangiogenesis also occurs around the iBALT structure during sustained inflammation [64]. iBALT participates in the pathogenesis of mucosal inflammatory diseases in a couple of ways: Antigen-presentation and T cell-priming can occur directly in iBALT in response to antigens derived from the airways; [65], and antigen-specific memory T cells can be maintained in iBALT as CD4 + T RM cells, which react efficiently to secondary immune responses [9,66] Thus the formation of iBALT is closely associated with the pathology of various inflammatory diseases. For example, the formation of iBALT is observed in the lungs of patients with chronic obstructive pulmonary disease, and the disease severity is correlated with the amount of iBALT in the lung [67]. iBALT formation can also be observed in the lungs of patients with rheumatoid arthritis or Sjögren syndrome [68]. Furthermore, the Th2 cell-associated immune response in experimental settings, such as house dust mite driven airway inflammation or ovalbumin-induced chronic allergic airway inflammation, can induce iBALT structures in mice [9,69].
Why is the BALT lymphoid tissue important?
Bronchus-associated and nasal-associated lymphoid tissues (BALT, NALT) are of special importance because of their rapid and continual exposure to airborne particulate antigens and microorganisms from the external environment.
How are tertiary lymphoid tissues formed?
Tertiary lymphoid tissues resemble secondary lymphoid tissues in many respects but are formed in the adult in response to chronic inflammation in locations where such tissues do not exist in steady-state conditions. The induction of tertiary lymphoid tissues can be compared with the formation of lymph nodes during normal development. Normal lymph node development involves the colonization of connective tissues in characteristic vascular nexuses by RORγt-dependent, CD4+, lymphotoxin-positive lymphoid tissue inducer cells. 93 These cells use surface lymphotoxin and TNF to induce local stromal cells to express ICAM-1 and VCAM-1 and produce CCL19/21 or CXCL13, leading to development of lymph node stroma with a reticular fiber conduit system that is integrated into the developing lymphatic vessel system. Thus steady-state presentation of inflammatory cytokines plays a key role in this process. This normal process can also be recapitulated in the adult because chronic inflammation induces production of TNF and lymphotoxin in normal tissues, leading to the induction of stromal cells to form organized follicles and T cell zones within the inflamed tissues. Induction of stromal cells to produce CCL19/21 and/or CXCL13 is probably important in this process because transgenic expression of CXCL13 in ectopic locations in mice leads to the formation of fully developed B cell follicles in these tissues. 94 Thus B cells may have a particular capacity to induce tertiary lymphoid tissues. The efficacy of anti-TNF therapies in autoimmune disease may relate to the suppression of such tissues. 95
Which tissue is the topographical relationship between the pineal gland and the lymphoid cells?
The topographical relationship between the cells of the pineal gland and lymphoid cells is identical to that in the lymphoepithelial tissue ( Oláh and Glick, 1983 ). From the wall of the pineal vesicles, the lymphoid cells can enter the lumen of the vesicles.
Is the trachea a constitutive lymphoid tissue?
Constitutive lymphoid tissue has not been described in the avian trachea. However, infection models with Mycoplasma gallisepticum have shown that the tracheal mucosa is highly responsive to infections and reacts with extensive lymphocyte infiltration followed by lymphoproliferation ( Gaunson et al., 2000, 2006 ). CD8 + cells are found in clusters or lymphoid follicle-like structures within the tracheal mucosa while CD4 + cells are spread randomly. Tracheal lesions characteristic for Mycoplasma infections predominantly consist of proliferating B cells ( Gaunson et al., 2006 ). Similar responses in the tracheal mucosa have been observed after infection with infectious bronchitis virus (IBV). Production of IBV-induced lesions is associated with massive lymphocyte infiltration in the tracheal lamina propria, the generation of numerous lymphoid follicles and the immigration of plasma cells ( Kotani et al., 2000a, b ). Interesting findings have been provided in a study by Javed et al. (2005), who compared immune responses to M. gallisepticum infection in the trachea between vaccinated and unvaccinated chickens. While unvaccinated chickens had infiltration of large numbers of B and T cells and some plasma cells, vaccinated birds developed secondary lymphoid follicle-like aggregates with far fewer lesions. In addition, in tracheal tissue of vaccinated birds manifold more mycoplasma-specific ASC could be identified than in unvaccinated animals. This indicates that the tracheal mucosa lymphoid tissue can be induced by different infections.
What is the role of lymphoid organs in the development of immune cells?
Lymphoid organs are defined as those organs where the maturation and proliferation of lymphocytes take place. They also play a very important role in the development of immune cells and also act as the checkpoints of foreign substances.
What are the primary lymphoid organs?
I. Primary lymphoid organs are those organs where B and T-lymphocytes mature and acquire antigen-specific receptors. II. These organs are the sites of origin and proliferation of lymphocytes. Thus, they are also called central lymphoid organs.
What is the immune system made of?
Lymphoid Organs: Do you know what our immune system is made up of? Can you name one organ or a body part that protects our body from pathogens? Our immune system is made up of many individual cells, tissues, proteins (antibodies), along with many organs called lymphoid organs. The Lymphoid organs are the sites where the maturation and proliferation of lymphocytes take place and also help in carrying out various immune functions. Lymphoid organs form a part of the lymphatic system that is composed of lymphatic vessels, lymph nodes, and lymph.
Which organs are involved in the production of blood cells?
2. The primary lymphoid organs, i.e., the bone marrow and thymus, are the sites where the proliferation and maturation of B-lymphocytes and T-lymphocytes take place. 3. Bone marrow is involved in the production of blood cells, i.e., RBCs (or erythrocytes), WBCs (or leucocytes) and Platelets (or thrombocytes).
Which organs are specialized tissues that provide the typical anatomic location and microenvironment?
Or in other words, the Lymphoid organs are specialized tissues that provide the typical anatomic location and microenvironment, which helps in attaining maturity of lymphocytes and thus, activates them. Lymphocytes are a type of WBC (leucocytes) that are the main components of our immune system.
What is the function of the spleen?
4) The spleen is involved in the synthesis of antibodies in its white pulp. By way of blood and lymph node circulation, the spleen is also involved in the removal of antibody-coated bacteria and antibody-coated blood cells.
What are the two types of lymphocytes?
Lymphocytes are a type of WBC (leucocytes) that are the main components of our immune system. There are two types of lymphocytes, T-lymphocytes, and B-lymphocytes.
Why can a lymph node be flushed?
1. Can be flushed into the lymph node because it was present in tissue fluids
Which lymphocytes are responsible for antigen dependent activation?
House naive lymphocytes. Funnel antigen to antigen-specific B and T cells to drive antigen dependent activation to effector and memory cells
Where does plasma cell produce antibody?
False. Plasma cells begin to produce antibody in the lymph node, and antibody enriched lymph is dumped into the bloodstream
Where do M cells form?
M cells form microfolds on the luminal surface and transport proteins and microbes from the intestinal lumen
